A semiconductor manufacturing apparatus has been known as an example of a substrate processing apparatus, and a vertical-type diffusion CVD apparatus has been known as an example of a semiconductor manufacturing apparatus. In such a substrate processing apparatus, when the substrate is processed, a heating apparatus is used to heat the substrate.
As an example of the heating apparatus, there has been known an apparatus having an annular side wall heat insulator installed outside a reaction container, a heating element installed on an inner surface of the side wall heat insulator, and a ceiling heat insulator installed above the side wall heat insulator, which heats a substrate within the reaction container by means of the heating element and supplies a cooling gas to a space between the reaction container and the side wall heat insulator to cool the heated substrate, in the related art. In such a heating apparatus, the cooling gas supplied to the space between the reaction container and the side wall heat insulator is discharged outside of the heating apparatus through the ceiling heat insulator.
In this type of the heating apparatus, however, since the cooling gas is discharged through the ceiling heat insulator, a gas-flow path for the cooling gas needs to be installed on the ceiling heat insulator. Thus, a difference in thermal insulation is caused depending on portions of the ceiling heat insulator to result in a degradation of in-plane temperature uniformity of the substrate.